图论（算法竞赛、蓝桥杯）--拓扑排序

1、B站视频链接：D01 拓扑排序_哔哩哔哩_bilibili

#include <bits/stdc++.h> 
using namespace std;
const int N=100010;
int n,m,a,b;
vector<int> e[N],tp;
int din[N];
bool topsort(){queue<int> q;for(int i=1;i<=n;i++){if(din[i]==0)q.push(i);}while(q.size()){int x=q.front();q.pop();tp.push_back(x);for(auto y:e[x]){if(--din[y]==0)q.push(y);}}return tp.size()==n;
}
int main(){cin>>n>>m;for(int i=0;i<m;i++){cin>>a>>b;e[a].push_back(b);//a到b的有向边din[b]++;//入度加一 }if(!topsort())puts("-1");else for(auto x:tp)printf("%d ",x);return 0;
}

#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;const int N = 100010;
int n,m,a,b;
vector<int> e[N], tp;
int c[N]; //染色数组bool dfs(int x){c[x] = -1;for(int y : e[x]){if(c[y]<0)return 0; //有环 else if(!c[y])if(!dfs(y))return 0;}c[x] = 1;tp.push_back(x);return 1;
}
bool toposort(){memset(c, 0, sizeof(c));for(int x = 1; x <= n; x++)if(!c[x])if(!dfs(x))return 0;reverse(tp.begin(),tp.end());return 1;
}
int main(){cin >> n >> m;for(int i=0; i<m; i++){cin >> a >> b;e[a].push_back(b);}if(!toposort()) puts("-1");else for(int x:tp)printf("%d ",x);return 0;
}